1. Field of the Invention
The present invention relates to a pad structure and a mounted structure.
2. Description of the Related Art
Conventionally, a printed circuit board is known that includes at least one insulating layer, two layers of circuit conductive layers formed at both surfaces of the insulating layer, respectively, and vias made of an electroless plating metal filled in via holes formed in the insulating layer for connecting the circuit conductive layers. In this printed circuit board, a part of at least one of the circuit conductive layers is formed by a sputtering method (see Patent Document 1, for example).
Meanwhile, conventionally, it is known that galvanic corrosion is generated when different kinds of metals are in contact with each other, depending on a combination of the metals.
Further, there is a risk that a via (a copper post) formed by an electroless plating, for example, is eroded due to the galvanic corrosion if different kinds of metals are in contact in the via, when removing an unnecessary part of the via by etching, in the conventional printed circuit board. If the via is eroded due to the galvanic corrosion, there may be problems such as where the via disappears, strength is lowered, electrical connection is worsened or the like.